Water reclamation process

ABSTRACT

Dirty process water collected from a process unit is held in a raw water holding tank. Air and process chemicals enter the system in this tank. Water from the tank passes at a uniform rate through a flotation cell where solids are frothed by flocculation and aeration and removed. Makeup water saturated with air and at a lower temperature than the process water liberates air in the cell as part of the aeration. Air dissolved in the tank provides further aeration in the cell. Water from the cell is held in a treated water holding tank and uniformly withdrawn from the tank to a filter for the removal of more solids. Filtered water is stored in a filtered water storage vessel for use in the process facility. Heat exchange keeps the filtered water at required temperature. Water discharged from the system to a sanitary sewer may have various degrees of purity.

This is a continuation of application Ser. No. 744,170, filed Nov. 22,1976, now abandoned; which is a continuation of Ser. No. 585,062, June9, 1975, abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to water treatment in general, and, inparticular, to a reclamation process particularly for use in laundryfacilities for the removal of solids from laundry wash water.

In many areas of the country the cost of water and its availabilitymakes it necessary to conserve this resource as much as possible. Inaddition, sewage facilities are often overtaxed. Accordingly, it isbecoming the practice to recycle or reclaim water for reuse.

Commercial laundries use a considerable amount of water. This waterbecomes dirty because of solid soil from the wash. For water reclamationin such facilities, it is necessary to effectively and economicallyremove a significant amount of the solids from raw wash water.

Solids can be removed from laundry water in flotation cells. In a cell,solids agglomerate with a flocculating agent and the agglomerates attachto air bubbles. The agglomerates are removed, say, by skimming. Solidscan also be removed in a filter which traps the solids and separatesthem from laundry water. One problem with these removal techniques isthat each requires a uniform rate of dirty water input for optimumperformance and the dirty water is not generated at the same rate oruniformity. Moreover, and compounding the problem, is the requirementthat treated water be available for laundry usage. While theconservation of water is itself laudable, the purity of any waterdischarged to sewage can also be important.

Additives for water conditioning are often required and these should beput into the reclamation system where good mixing occurs. The flotationcell supply of air bubbles traditionally comes from a pressure reductionof air tending to come out of solution as pressure is lowered.

SUMMARY OF THE INVENTION

The present invention provides a water reclamation process especiallyfor use in facilities, such as laundry facilities, to take suspendedsolids from dirty water and make the water suitable for reuse. Theprocess does this in a balanced system where a flotation cell and filterare fed water at uniform and optimized rates. In the flotation cell, aircomes out of solution in water because of pressure drop and temperatureincrease. Temperature increase results in feeding relatively cool makeupwater with dissolved air into the cell where it mixes with warmerprocess water.

In general, the present invention contemplates taking raw, dirty waterand accumulating it in a waste water holding vessel where it accumulatesto supply a flotation cell at a constant rate. In the flotation cellflocculating agents and aeration remove suspended solids. Aerationresults from air coming out of solution in the water. Makeup water forthe system is at a lower temperature than the water being reclaimed.This fact allows makeup water heavy with dissolved air to be introducedinto the flotation cell where it mixes with the warmer water there. Withan increase in temperature the dissolved air comes out of solution asbubbles. The standard means of release of dissolved air by pressurereduction is also preferably used. Treated water from the cell is thenpassed into a partially treated water storage vessel where it canaccumulate and supply a filter at a uniform rate. The filter removesfurther solids. Means are provided to terminate and initiate flow fromthe vessels when there is insufficient water in them to supply theirserviced units at a sufficient rate and quantity and to initiate flowwhen adequate levels are reached. Preferably filtered water is stored ina vessel for use in a process facility, such as washers in a laundry. Itis preferred that the stored vessel be maintained at a temperaturesuitable for the process of the facility so that when water is demandedit need not be heated first.

Air introduced into the waste water holding vessel is dissolved in thewater there for release in the flotation cell. Water treatment chemicalscan be introduced into the same vessel to take advantage of the mixingoccurring during the introduction of the air.

Waste water collected and stored in the holding vessel is withdrawn fromthe vessel at a rate corresponding to the rate capacity of the flotationcell. Thus the holding vessel assures sufficient water input to the cellto satisfy its rate demand. The flotation cell is of the type from whichdissolved air is released from solution and bubbles up through the cell.These bubbles collect agglomerated solids to form a froth which is thenremoved. Bubble release is by both a drop in pressure and an increase intemperature. The makeup water addition in the flotation cell, therefore,allows advantage to be taken of its relatively low temperature. Treatedwater from the flotation cell accumulates in the treated water storagevessel and when there is a predetermined amount of such water it istaken off at a uniform rate for filtration and further purification fromsolids.

When the filter needs cleaning, a sensor may measure pressure dropacross it which corresponds to a maximum amount of waste solids in thefilter and initiate a backwashing operation to clean the filter. It ispreferred that this backwash water be recycled through the flotation andfiltration processes by being sent to the waste water holding vessel.

Water discharged from the system to a sanitary sewer may readily betreated to a desired degree of purity. When a degree of purity more thanthat obtainable by the flotation cell alone but less than thatobtainable by both the cell and filter is required, it is preferred thatdischarge be taken downstream from both the flotation cell and filter.This enables uniform feed into the purification components without largecomponents. To take off only after the filter, for example, wouldrequire larger components because the filter would have to have a biggercapacity.

In laundry applications it is preferred to maintain the pH of the waterfrom about 6.5 to about 12. This pH, once attained, remains unchangedthroughout the process. Again in the laundry applications it is desiredto have an active alkalinity level, active in the sense that there areingredients which effect cleansing action of the water. An activealkalinity level, however, often varies from essentially zero to 1500parts per million. It is preferred to have a pH of about 10.5 and anactive alkalinity of 250 ppm in the clean water.

If the waste suspended solids become too great, say about 3500 ppm, itbecomes extremely difficult to treat the water by the process of thepresent invention. It is therefore preferred to combine waste streams insuch a manner so as to produce a composite having about 500 ppm or lessof suspended solids. Treated and filtered water has a purity of 20 ppmof suspended solids or less.

It has been found that a short chain cationic polymer is an idealflocculating agent. An anionic polymer does not seem to work. It seemsthat an anionic short chain polymer does not disperse well and remainsin globules.

If desired, the water being treated by solid removal can also besterilized. This is preferably downstream of the flotation cell andupstream from the treated water storage vessel. The initiation ofsterilization at this location gives time for the sterilizers to workwhen they are chemical because of the holding time in the treated waterstorage vessel.

Other flocculating agents such as members of the alum family could beused but these types of flocculating agents reduce water pH.

These and other features, aspects and advantages of the presentinvention will become more apparent from the following description,appended claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow schematic of one preferred process and system of thepresent invention;

FIG. 2 is a flow schematic similar to the FIG. 1 embodiment with amodification;

FIG. 3 is a flow schematic similar to the FIG. 1 embodiment with asecond modification; and

FIG. 4 is a flow schematic similar to the FIG. 1 embodiment with a thirdmodification.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to the FIG. 1, a processing unit 10, say a series ofwashing units, generates raw, dirty water having a solid particlecontent which must be removed for water recycling. Solid removal to alevel of about 20 ppm or lower is typically necessary. This raw, dirtywater is collected from the process unit in a line 11 for delivery to acollection tank 12. A dump line 13 from tank 12 permits the discharge ofsome waste water directly into a sanitary sewer. A float control in thistank determines when water is pumped by a pump 14 through a line 16 intoa raw waste water holding vessel or tank 18. A check valve 20 in theline permits flow of raw water only from the collection tank to theholding tank. A control valve 21 controls the flow of raw water throughline 16 and is open during water treatment.

A normally closed float switch 23 in holding tank 18 terminates waterflow from collection tank 12 to tank 18 when a predetermined amount ofwater is in the holding tank by opening and turning off pump 14.

A line 19 delivers and injects compressed air into raw water storagetank 18 for the aeration and mixing of waste water there. Air diffusioninto the water in the tank may be by a perforated pipe. Some of the airdissolved in the water is released in a flotation cell 22 as bubbles toaid in the collection of waste solid agglomerates.

Flotation cell 22 provides a first stage of solid removal. Thisflotation cell is in series with holding tank 18 through a line 24. Line24 has a control valve 26 upstream from a pump 28. A check valve 30 inthe line is downstream from the pump but upstream from the flotationcell, and permits flow only in the direction of the flotation cell.Another control valve 32 is in line 16 between check valve 30 and theflotation cell.

A normally open float switch 33 in holding tank 18 controls pump 28.When there is sufficient water in the holding tank, the float switchcloses and turns pump 28 on to deliver water to the flotation cell. Whenthere is a predetermined low amount of water in tank 18, the same floatswitch turns off pump 28. Valve 32 controls the rate of pumping fromtank 18 to maintain a continuous flow of raw water into and throughflotation cell 22 at the current level of raw water input forpurification. Check valve 30 prevents water from flowing towards tank18. Valve 26 permits control of water into the pump.

Flotation cell 22 is known as such. A satisfactory cell is described inU.S. Pat. No. 3,175,687. Raw water from line 24 is aerated by anaeration pump in the cell. Air dissolved in water is introduced into thecell and comes out of solution because of a drop in pressure. Makeupwater enters the system through a line and source 44 into the flotationcell. Makeup water enters here to take advantage of its air solventpotential. The makeup water is at a low temperature compared with waterfrom process 10, say 70° F. compared with 120° F. This fact means thatmore air can be carried by the makeup water than by the process water.Stream 44 is saturated with air and some of this air comes out ofsolution in cell 22 as bubbles because the makeup water is heated byprocess water in the cell. These bubbles augment those from a drop inpressure, which also occurs to the makeup water.

A line 39 from a source of flocculents 40 supplies the flocculants usedfor solid removal from the water in the cell. In addition to theintroduction of flocculants from source 40 through line 39 in flotationcell 22, chemicals may be added into the waste water holding tank asfrom a source and line 42. The addition of chemicals at this latterlocation takes advantage of air mixing because of air introduced throughline 19. Chemical additives at 41 may be (a) flocculation aids such asactivated silica, clays or polyelectrolytes; (b) buffers such assulfuric acid; and (c) conditioning chemicals such as hydrated lime(CaOH₂) and soda ash (Na₂ CO₃).

Treated water from cell 22 passes through a line 42 and into a partiallytreated water surge vessel or tank 46.

A short chain cationic polymer flocculating agent or agents are meteredinto cell 22 from source 40 and through line 39, as previously stated.The flocculating agents cause the soil and solid particles to adhere toeach other. The resultant agglomerates attach to air bubbles producedupon release of air from the water with decreased pressure andtemperature. These bubbles and attached agglomerates rise to the surfaceof the cell as a foam or froth. The foam or froth is removed from thecell through a line 43. A shaker screen 45 concentrates solids from theeffluent. The concentrated solids are conveyed away to a bin, pile orother acceptable storage facility prior to disposal by a screw conveyor47.

Prior to entrance into treated water storage vessel 46, the water may besubjected to sterilization, preferably a chemical sterilizer such asfluorine, chlorine or ozone.

Treated water from the flotation cell passes through line 42 intopartially treated water storage vessel or tank 46. A normally open highlevel float switch 55 in tank 46 activates a pump 56 in a line 58leading from tank 46 to a mixed media filter 60 to pump water into thefilter when the water in the tank reaches a predetermined high level andcloses the switch. A normally closed float level switch 57 at apredetermined low water level within tank 46 stops pump 56 to stop waterflow through line 58 to the filter when this lower switch opens becauseof insufficient water.

Another normally closed float level switch 59 in tank 46 deenergizespump 28 when the level of partially treated water in tank 46 reaches apredetermined level. This is a precaution to prevent the level ofpartially treated water from becoming excessive in the tank bypreventing the generation of such water in flotation cell 22.

Line 58 has a valve 61 and a valve 62 upstream and downstream of pump56, respectively. The line also has a flow meter 64 and a flow indicator66 to indicate that flow is occurring in the line. Flow control valve 68in line 58 determines flow of water through the line into the filter. Acheck valve 69 prevents backflow in the direction of pump 56. Anothervalve 70 in the line downstream from the flow control valve togetherwith valve 62 permits the isolation of flow meter 64, flow indicator 66and flow control valve 68.

Partially treated water from line 58 enters the top of filter 60 througha series of dispersion nozzles and flows down through a mixed media bedin the filter. The filter media is of different materials with differentsizes and specific gravities. A suitable gradated bed is of small sizeparticled garnet sand at the bottom, medium size silica sand particlesin the middle, and large size anthracite particles at the top. Thegarnet sand has a specific gravity of 4.2, the silica sand has aspecific gravity of 2.6 to 2.7, and the anthracite has a specificgravity of 1.5. Filtered water from filter 60 passes through a line 72into a treated water storage vessel or tank 74. A valve 75 in line 72controls the flow of water through the line.

Filter 60 is periodically cleaned in response to a predetermined maximumpressure differential between its input and output. As waste solidsaccumulate in the filter, the pressure drop across it increases to thepredetermined maximum. In response to such a pressure differential thefilter is backwashed with water from treated water storage vessel 74 bya pump 76 in a line 77. The duration of backwash is controlled by anadjustable timer. Each backwash may be recorded on an automatic timer.Alternatively, or in addition to the differential pressure initiatedbackwash, backwashes can be pre-scheduled by means of an adjustabletimer or initiated by a push button. Backwash water is returned to rawwater storage vessel 18 through a line 78. A flow control valve 79 inline 77 controls the flow rate of backwash water into the filter. A pairof valves 80 and 81 straddle flow control valve 79 and are opened inresponse to the pressure differential which initiates backwash. Valve 75is closed during backwash. A valve 73 in line 78 is open only duringbackwash. Valve 70 is closed during this time and, of course, pump 56 isstopped.

Surfactants and solvents from a source 87 pass through a line 88 intoline 77 for cleansing the filter media in filter 60 of grease and oilduring backwash.

Thus, interlocks are provided to assure that the filter is notbackwashing and filtering at the same time. There may be air ventsprovided in the filter to remove air introduced with water. Air ispreferably added to the backwash water, as through an eductor 89discharging into line 77. This air agitates the sand filtering media foreffective washing.

During backwash, water and air mix the media and remove solids. Thesolvents and surfactants remove oil and grease. Gravity stacks the mediawith the heaviest material on the bottom of the filter.

Fully treated and filtered water is stored in tank 74. Pump 76 runsconstantly to supply a pressure head to a return line 82 to processingunit 10. The output of pump 76 goes through a line 83 to a heatexchanger 84, which is automatically controlled to heat water to apreset temperature. A control valve 91 in line 83 determines the flowthrough the line. A stream of water is continually diverted back to tank74 through a line 85 from the heat exchanger. This flow is controlledmanually by a control valve 86 in line 85 so that the tank contents arecontinually passing through the heat exchanger and being brought up tothe required temperature for washing. In this manner the entire contentsof tank 74 are maintained within a preset temperature range and readyfor demand in processing unit 10. Accordingly, a much smaller heatexchanger may be used than would be required for instantaneous heat-up.

A check valve 96 in line 82 prevents flow from the processing unit. Avalve 97 in the line controls flow to the processing units.

A check valve 98 in line 83 allows flow in the line only to heatexchanger 84. A valve 99 in the line controls the rate of flow from pump76 to heat exchanger 84. Heat exchanger 84 gets its heat energy forheating from steam provided through a line 100. A thermostaticallycontrolled valve 102 sensitive to the temperature of water in line 85determines the amount of steam needed. A valve 104 also controls theflow of steam.

The electrical controls for the operation of the system have beenincidentally called out earlier in this description. The attendantcircuits are shown schematically and abbreviated in the Figures, and thecontrolled pumps are shown separately from their depictions in the fluidcircuit to avoid confusion. The electrical circuit includes a source ofpower 130. An on-off switch 132 in a line 134 controls whether currentflows to the various pumps. Switch 33 is in series with source 130 andpump 28 in a line 136. Switch 23 is in series with pump 14 and thesource of power through a line 138. Switches 57 and 55 are seriallyconnected in a line 140 between the power source and pump 56. Switch 59serially connects pump 28 to power source 130 through a line 142.

The present invention optimizes the efficiency of the flotation cell bytaking advantage of the relatively low temperature of makeup water. Thiswater, saturated with air, liberates substantial amounts of the air whenheated by process water. This liberation augments bubble release bypressure reduction and together provides the bubbles for solidagglomeration. The use of temperature leverage combines with the feedingof the flotation cell and the mix media filter at each unit's requiredflow rate for continuous operation. Yet the vagaries of raw wash watergeneration and fresh wash water demand are met through the variousholding vessels. Tank 18 stores raw waste water from the washingfacility and backwash for processing in flotation cell 22. If there isinsufficient raw water to satisfy the capacity and throughput raterequirements of the cell, float switch 33 prevents delivery of water tothe cell. When the capacity of tank 18 is in danger of being exceeded,switch 23 stops raw wash water feed. Intermediate tank 46 has high andlow water controls in switches 55 and 57. When there is insufficientwater in the tank because of insufficient input from the flotation cell,the filter will not be supplied because switch 57 opens. Switch 55 doesnot close the circuit to filter makeup water pump 56 until there issufficient water for the filter. When there is danger of exceeding thecapacity of tank 46, switch 59 stops pump 28 and prevents raw wash waterfeed to its storage tank. Thus, there is a system whose components caneach operate optimally at different rates and which providesready-to-use treated wash water for the demand of a laundry facility,the latter demand satisfaction being described earlier.

Typically, raw water from the processing unit 10, say washingfacilities, is collected at a temperature ranging from city watertemperature of about 60° F. to hot water at about 180° F. Typically, theaverage temperature is about 120° F. The pH of the raw water ranges from6.5 to 12 and remains unchanged throughout the process just described.The active alkalinity level also varies widely from zero to 1500 ppm andremains unchanged throughout the process. It is preferred that theactive alkalinity level be about 250 ppm and that the pH be about 10.5.The higher the alkalinity level the more soil removed from wash.

It has been found that suspended solids in the waste water vary fromabout 20 to about 3500 ppm. In the latter concentrations it is difficultto treat the water. Accordingly, waste streams are preferably combinedin such a manner as to produce a composite having about 500 ppm or lessof suspended solids. The purification process and system of the presentinvention purifies the waste water to a solid content of about 20 ppm.The flotation cell removes about 80% of the suspended solids and thefilter removes about 80% of the solids remaining after flotation.

Filtration is not sensitive to temperature. Usually the temperatureduring filtration is about the same as the collected raw wash water,typically about 120° F. The finally treated water is typically raised toabout 190° F. for its introduction into the wash cycle.

The flocculating agent is a short chain cationic polymer added to theflotation cell at a rate of from between about 0.25 and about 1.0 agallon per hour as diluted to 1% strength.

FIG. 2 is a modification of the embodiment of FIG. 1. The components ofthe FIG. 2 embodiment which are the same as the FIG. 1 embodiment areidentified with common reference numerals. The difference is that no rawwater is discharged prior to treatment as it is in the FIG. 1 embodimentthrough line 13 from raw water collection tank 12. Instead, fullytreated water is removed after filter 60. A line 150 from filterdischarge line 72 goes to a sanitary sewer. A flow control valve 151 inline 150 determines the amount of discharge. This embodiment providesmaximum discharge water purity.

Like the embodiment of FIG. 2, the embodiment of FIG. 3 has many of thesame components as the embodiment of FIG. 1. Accordingly, commonreference numerals are used. The difference is that water is dischargedfrom the unit with solid removal only at flotation cell 22 anddischarged into a sanitary sewer. Thus, insofar as discharged water isconcerned, the FIG. 3 embodiment is intermediate the FIGS. 2 and 3embodiments. Discharge is immediately downstream of flotation cell 22 bya line 155 branching off line 42. Flow into line 155 is controlled by avalve 157.

FIG. 4 blends the water discharge of FIGS. 2 and 3. Again components arein common with FIG. 1 and are identified with the same referencenumerals. Discharge of water to a sanitary sewer occurs after filter 60in the manner of FIG. 2 through line 150 and a control valve 151 in theline. In addition, water for discharge is taken immediately downstreamof flotation cell 22 from line 42 by way of a line 159. A valve 160 inline 159 controls flow through it. Line 159 joins line 150 to thesanitary sewer. This embodiment offers the advantage of processstabilization. Considering that the filter and flotation cell havedifferent demands, water can yet be fed to the system uniformly and havethe required degree of purity in the discharge water without largepurification components.

The present invention has been described with reference to certainpreferred embodiments. The spirit and scope of the appended claimsshould not, however, necessarily be limited to the foregoingdescription.

What is claimed is:
 1. A process for the purification of waste water bythe removal of suspended solid waste therefrom comprising the stepsof:(a) accumulating the waste water in a waste water holding vessel toobtain a first predetermined initiation threshold quantity thereof; (b)introducing waste water from the waste water holding vessel into aflotation cell at a first continuous and predetermined rate after thefirst predetermined initiating threshold quantity is present in thewaste water holding vessel, the first continuous and predetermined ratecorresponding to the rate and quantity requirements of the flotationcell; (c) dissolving air in makeup water at a temperature below that ofthe waste water in the flotation cell; (d) introducing the makeup waterinto the flotation cell and releasing air from solution in the makeupwater by the warming of makeup water by the waste water, the releasedair being released as bubbles, such waste water introduction into theflotation cell reducing the quantity of waste water in the waste waterholding vessel to a first predetermined small quantity of waste water;(e) agglomerating said suspended solid waste from the water in theflotation cell to produce partially treated water by adherence of thesuspended solid waste to the air bubbles; (f) removing the agglomeratedsuspended solid waste from the flotation cell; (g) terminating wastewater introduction into the flotation cell and the first predeterminedsmall quantity of such water is present in the waste water holdingvessel, the first predetermined initiating threshold quantity beingsufficient for the flow rate and quantity requirements of the flotationcell, the first predetermined small quantity corresponding to aninsufficient quantity of waste water for the flow rate and quantityrequirements of the cell; (h) accumulating partially treated water fromthe flotation cell in a partially treated water holding vessel to obtaina second predetermined initiating threshold quantity of partiallytreated water; (i) introducing partially treated water from thepartially treated water holding vessel into a filter at a secondcontinuous and predetermined rate after the second predeterminedinitiating threshold quantity is present in the partially treated waterholding vessel, such partially treated water introduction into thefilter reducing the quantity of partially treated water in the partiallytreated water holding vessel to a predetermined second small quantity ofpartially treated water, the second continuous and predetermined ratecorresponding to the rate and quantity requirements of the filter andbeing different from the first continuous and predetermined rate; (j)filtering water treated in the flotation cell in the filter to removeadditional suspended solid waste; (k) terminating partially treatedwater introduction into the filter when the predetermined second smallquantity of such water is present in the partially treated water holdingvessel, the second predetermined initiating threshold quantity beingsufficient for the flow rate and quantity requirements of the filter,the second predetermined small quantity corresponding to an insufficientquantity of partially treated water for the flow rate and quantityrequirements of the filter; and (l) recycling the filtered water to thesource of waste water.
 2. The process claimed in claim 1 including:(a)dissolving air in the waste water prior to the agglomeration step in thewaste water holding vessel; (b) releasing dissolved air in the wastewater during the agglomeration step to produce additional air bubbles;(c) flocculating the water in the flotation cell during theagglomeration step to produce the agglomerates of said suspended solidwaste; and (d) adhering the agglomerates to the bubbles, the removalstep removing the adhered agglomerates.
 3. The process claimed in claim2 including the step of terminating waste water accumulation in thewaste water holding vessel when a predetermined maximum quantity ofpartially treated water is in the partially treated water holdingvessel.
 4. The process claimed in claim 3 including the steps of:(a)storing the filtered water in a storage vessel before the recyclingstep; and (b) heating the stored water to within a predeterminedtemperature range for immediate use in a wash cycle of a laundryprocess.
 5. The process claimed in claim 3 wherein the flocculatingagent is a short chain cationic polymer.
 6. The process claimed in claim2 including discharging a portion of the waste water to sewage prior tothe introduction step.
 7. The process claimed in claim 2 includingdischarging a portion of the filtered water to sewage prior to therecycling step.
 8. The process claimed in claim 2 including discharginga portion of the partially treated water to sewage.
 9. The processclaimed in claim 2 including:(a) discharging a portion of the filteredwater to sewage prior to the recycling step; and (b) discharging aportion of the partially treated water to sewage.
 10. A process forrecycling waste water containing suspended solid waste comprising thesteps of:(a) collecting said waste water from a source thereof in awaste water holding vessel; (b) introducing the collected waste waterinto a flotation cell at a first continuous and predetermined rate whenthere is a first predetermined large quantity of such water in the wastewater holding vessel, such waste water introduction into the flotationcell reducing the quantity of waste water in the waste water holdingvessel to a predetermined small quantity of such waste water, the firstcontinuous and predetermined rate corresponding to the rate and quantityrequirements of the flotation cell; (c) terminating the introduction ofcollected waste water into the flotation cell when there is the firstpredetermined small quantity of such water in the waste water holdingvessel; (d) collecting said suspended solid waste from the waste waterin the flotation cell by flocculation and aeration to form agglomeratesof said suspended solid waste adhered to air bubbles produced byaeration, the aeration being by the release of dissolved air by(i)pressure reduction in the flotation cell, and (ii) temperature increaseof makeup water introduced in the flotation cell by heat exchange withwaste water there; (e) removing the agglomerates from the flotationcell; (f) collecting water treated from the flotation cell in apartially treated water holding vessel; (g) introducing the partiallytreated water from the holding vessel into a filter at a secondcontinuous and predetermined rate when there is a second predeterminedlarge quantity of such water in the partially treated water holdingvessel, such partially treated water introduction into the filterreducing the quantity of partially treated water in the partiallytreated water holding vessel to a predetermined small quantity of suchpartially treated water, the second continuous and predetermined ratecorresponding to the rate and quantity requirements of the filter andbeing different from the first predetermined and continuous rate; (h)terminating the introduction of partially treated water from thepartially treated water holding vessel into the filter when there is thesecond predetermined small quantity of such water in the partiallytreated water holding vessel; (i) the first and second predeterminedlarge quantities of water in the waste water holding vessel andpartially treated water holding vessel corresponding to quantities ofwater sufficient to supply the flotation cell and filter, respectively,at predetermined flow rates and quantities, the first and secondpredetermined small quantities in such vessels corresponding toinsufficient water for such flow rates and quantities; (j) filteringwater in the filter; (k) collecting filtered water in a treated waterstorage vessel; and (l) recycling the filtered water from the treatedwater storage vessel as feed to the source.
 11. The process claimed inclaim 10 including the step of sterilizing partially treated water fromthe flotation cell.
 12. The process claimed in claim 11 including thestep of periodically backwashing the filter with water from thecollected water storage vessel.
 13. The process claimed in claim 10wherein flocculation is accomplished with a short chain cationicpolymer.
 14. The process claimed in claim 10 including the steps oftreatment chemical addition into the waste water holding vessel andaerating the waste water in the waste water holding vessel.